#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=2167167167167167167;
const int INF=2100000000;
const ll mod=998244353;
#define rep(i,a) for (ll i=0;i<a;i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}
template<class T> void vec_out(vector<T> &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}



void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	int N,M;
	cin>>N>>M;
	vector<string> S(N);
	rep(i,N) cin>>S[i];
	int ans=0;
	rep(i,2){
		swap(S[0],S[1]);
		string T;
		int a=0,b=0; 
		rep(i,M+1){
			if(a==M) T+=S[1][b],b++;
			else if(S[0][a]==S[1][b]) T+=S[0][a],a++,b++;
			else if(a==b) T+=S[0][a],a++;
			else T+=S[1][b],b++;
		}
		if(a!=M||b!=M) continue;
		int J=0;
		rep(i,N){
			a=0;
			rep(j,M+1){
				if(T[j]==S[i][a]) a++;
				if(j==M&&a!=M){
					J=1;
				}
			}
		}
		ans++;
		ans-=J;
	}
	cout<<ans<<"\n";
}